Dynamic environment but no temperature change since the late Paleogene at Lühe Basin (Yunnan, China)

Abstract

The complex tectonic evolution in the Tibetan region has impacted climate, the Asian monsoon system, and the development of major biodiversity hotspots, especially since the onset of the India-Eurasia continental collision during the early Paleogene. Untangling the links between the geologic, climatic, and ecological history of the broader region provides insights into key Earth system mechanisms, relevant for understanding our rapidly changing planet. Notably around this time, the Eocene-Oligocene transition (EOT; ∼34 million years ago, Ma) marked a critical shift from a greenhouse to an icehouse climate. Whereas temperatures derived from benthic marine records show ubiquitous global cooling of 4 °C, there is an emerging picture that sea surface temperatures and the terrestrial realm experienced a heterogenous response across this interval. Here, we reconstruct a terrestrial temperature record from ∼35–27 Ma at a tectonically unresolved location at the margins of the Tibetan Plateau, Lühe Basin (Yunnan, China). Our multi-proxy organic geochemistry approach across a 340-m long section, complemented by sedimentological interpretations, climate model results, and palaeobotany-based estimates at a nearby site, shows that Lühe Basin hosted a dynamic fluvial environment that maintained relatively stable average temperatures across this 8-million-year interval. The lack of cooling at Lühe Basin supports evidence that sea surface temperatures and terrestrial sections had a complex and heterogenous response across the EOT despite the ubiquitous 4 °C cooling trends seen in the benthic marine record. Furthermore, these palaeotemperature estimates match present-day values at this location, suggesting that this area has not undergone significant temperature change – and possibly no significant uplift – since the late Paleogene.